A second subject of the present disclosure is a multi-component package unit (kit-of-parts, or also kit) containing two separate agents packaged separately in at least two containers, which are applied in the aforementioned method. The kit-of-parts comprises a first container which contains a hydrous acidified pre-treatment agent. The coloring agent, which contains at least one acid dye and one neutral to basic pH value is contained in a second container.
Changing the form and color of keratinous fibers, more particularly of hair, constitutes an important area of modern cosmetics. Consequently, the hair's appearance can be adapted both to current fashion trends and also to the particular preferences of each and every person. In order to change the hair color, the person skilled in the art knows various staining systems depending on requirements for the coloration. Oxidation coloring dyes are usually used for permanent, intense coloring with good fastness properties and good coverage of gray. Such colorants usually contain oxidation dye precursors, so-called developer components and coupler components, which form the dyes under the influence of oxidants, such as hydrogen peroxide. Oxidation dyes are exemplified by outstanding, long-lasting coloring results, but are also associated with a certain amount of hair damage. With an emphasis particularly on low-damage coloring, therefore, use of oxidation dyes is not the first method of choice.
The color of hair can be changed temporarily by employing partially-oxidizing dyes. In this process, dyes already formed diffuse from the colorant into the hair fibers. In comparison oxidative hair coloring, the colors obtained with partially-oxidizing dyes has lower stability and washes out more quickly.
The gray coverage that can be achieved with partially-oxidizing dyes is generally in need of improvement. However, the low hair damage of dyeing with partially-oxidizing dyes is advantageous.
There are various substance classes available to the person skilled in the art for coloring with partially-oxidizing dyes, such as nitro dyes, anthraquinone dyes, azo dyes or triarylmethane dyes. Furthermore, it is also possible to classify dyes in different categories depending on their charge. Dyes with a cationic charge are usually referred to as “basic dyes”; a person skilled in the art knows dyes with an anionic charge by the term “acid dyes”.
Acid dyes within the group of partially-oxidizing dyes have the best fastness properties. However, the coloring effect of acid dyes depends heavily on the pH value. In order to achieve an intense color result, the agents applied on the keratinous fibers must usually have a pH value of less than about 5. A pH value of less than about 3 is particularly preferred.
A disadvantage of acid dies is their often very pronounced skin coloring. In this case, the coloring of the hair and the skin coloring occur in parallel. The more intense the hair color, the stronger the skin coloring usually is on all body parts that come into contact with the coloring agent during the dyeing process.
Therefore, the present disclosure addresses the problem of reducing skin coloring during dyeing with acid dyes.